Method for monitoring proper fastening of an article of assembly at more than one location

ABSTRACT

A more reliable and fool-proof method and apparatus for assembling an article of assembly (e.g. with predetermined screw torque requirements) in which the article of assembly has multiple fastening locations. The method comprises holding the article of assembly fixed while providing at least two different types of targets fixed relative to the article of assembly that correspond to the individual fastening locations. Fasteners are fastened into the article of assembly at the fastening locations. When fastening is occurring at one of the fastening locations, one of the targets is being sensed. Based on the target sensed, a target output is generated that differentiates between different types of targets thereby indicating fastening location of the fastening tool. The electronic target output is used for electronic control such as for stopping a conveyor to keep the article of assembly at an assembly station until the fastening operations have been completed.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a reissue application of U.S. Pat. No.7,062,831, issued Jun. 20, 2006, on application Ser. No. 10/789,307,filed Feb. 27, 2004, which was a divisional of U.S. patent applicationSer. No. 09/992,326, filed Nov. 19, 2001, now U.S. Pat. No. 6,763,573.

FIELD OF THE INVENTION

The present invention relates generally to assembly systems, and moreparticularly relates to monitoring fastening of articles of assembliesin such assembly systems.

BACKGROUND OF THE INVENTION

There are many industries where the sequence of fastening operationsand/or the applied torque of fastening operations are critical inassembling an article of assembly. One such particular industry is theautomotive seat assembly industry.

In the automotive seat assembly industry, if the fastening operation ofscrews on a seat frame is not performed correctly to fasten the parts ofthe seat together, then the assembled seat may be more prone to possiblefailure. Proper fastening of a screw may require a predetermined amountof torque to be applied to one or more screws or that the screws befastened according to a predetermined sequence, or possibly bothrequirements. It is also necessary that all of the fastening locationsbe properly subject to a fastening operation and filled with a fastener.

A common requirement in the seat industry is that certain criticalscrews need to be fastened with a predetermined amount of torque. Theamount of torque required for different screws among a seat can alsosometimes be different. Screw torque requirements can be so critical forcertain industries that monetary fines or disqualification ofmanufactured product can occur if certain critical screws that have notbeen properly fastened or torqued to the predetermined value.

In seat assembly operations, it is desirable to assembly a large volumeof seats on an assembly line. In modern systems, this is typicallyaccomplished with conveyor systems that carry seats held in fixturesthrough multiple assembly stations. Conveyor systems may be acontinuously moving line whereby seats are worked on and assembled asthe seats are moving and traveling down the line, or as an intermittentstop and go system whereby seats are temporarily stopped at each stationfor assembly operations and then conveyed down the line to the nextstation. At the stations where seat parts are assembled with screwsaccording to a predetermined torque, torque reaction arm drivers areused. Torque reaction arm drivers provide an indication of the amount oftorque applied during a fastening operation.

To achieve high volume assembly and to keep conveyor lines short,typically several different screws are fastened by a single worker at agiven assembly station along the line. For example, a common arrangementis a seat assembly station where several screws are installed into theseat requiring a predetermined applied torque of the same value. Thissystem includes a mechanism that keeps a seat at a station until thedesired number of torque values is achieved with the torque reaction armthat is equal to the number of screws being installed.

While the torque reaction arm is capable of providing an indication ofdriven torque, this type of system can be easily tricked or subject tofailure. In particular, if the worker of the torque reaction arm drivesthe same screw twice he can accidentally provide two torque values forone screw. In repetitive work operations requiring several tasks at asingle assembly station, workers can forget which screw has beenproperly fastened or otherwise make an accidental error in fastening thesame screw twice. The result is that one or more screws have beenimproperly fastened despite the total number of torque values has beenachieved for the station (thereby allowing release of the seat from thestation for further downstream assembly).

Even without mistakes, some workers have been known to intentionallybypass or trick existing systems. In particular, there have beeninstances where a worker drives a screw, then reverses the same screwand then refastens that same screw at the same location to get more thanone good output value at the same location to in effect trick thesystem. Workers have even been known drive a screw mounted in a panelproximate the assembly station to intentionally bypass or trick thesystem. The cause of these problems is difficult to understand but itmay include worker frustration or fatigue with respect to properlyfastening screws into a seat.

One approach to reducing employee mistakes in fastening operations is toreduce the number of tasks performed at a given work station. However,this approach increases the length and cost of the assembly line anddecreases worker efficiency. Another approach is to install qualitycontrol in the form of close supervision or downstream torque checkingto ensure quality and accuracy of fastening operations. However,increased supervision also increases costs and decreases overallefficiency of an assembly line. There have even been instances wherecompanies have discovered such fastening problems of a large scale leveland have had to conduct massive quality control operations by manuallychecking the proper installation of fasteners and thousands of torquevalues on seats that have already been run through the line. This isboth time consuming and costly.

BRIEF SUMMARY OF THE INVENTION

In light of the above, it is a general aim of the present invention toprovide a more reliable and more fool-proof way to conduct fasteningoperations in assembling an article of assembly.

In that regard, it is also a further object of the present invention toprovide a more efficient way of ensuring fastening operations areperformed correctly on an article of assembly.

In accordance with these and other objectives, the present invention isdirected towards a new more reliable method for assembling an article ofassembly in which the article of assembly having multiple fasteninglocations in spaced apart relation. The method comprises holding thearticle of assembly in a fixed position while providing at least twodifferent types of targets fixed relative to the article of assemblythat correspond to the individual fastening locations. Fasteners arefastened into the article of assembly at the various fasteninglocations. When fastening is occurring at one of the fasteninglocations, one of the targets is being sensed. Based on the targetsensed, an electronic target output is generated that differentiatesbetween the different types of targets thereby indicating fasteninglocation of the fastening tool. The electronic target output can be usedfor electronic control or alarm purposes.

The present invention is also directed toward an assembly system forassembling articles of assembly to implement the above method. Theassembly system comprises a fixture holding the article of assembly, andfirst and second targets fixed relative to the fixture that correspondto first and second fastening locations on the articles of assembly. Afastening tool is adapted to fasten fasteners into the article ofassembly at the first and second fastening locations with different toolpositions relative to the fixture when the tool is at the differentfastening locations. The assembly system further includes a targetsensor fixed relative to the fastening tool along at least one axis. Thetarget sensor senses the first and second targets when the fasteningtool is fastening at the first and second locations respectively. Thetarget sensor generates a target output differentiating between thefirst and second targets and thereby indicates when the fastening toolthe first and second fastening locations.

Further aspects of the present invention relate to implementations onconveyor systems including both continuous and non-continuous orintermittent type conveyor systems.

Other objectives and advantages of the invention will become moreapparent from the following detailed description when taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of thespecification illustrate several aspects of the present invention, andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is an isometric and partly schematic view of a seat assemblystation according to a preferred embodiment of the present invention.

FIG. 2 is a side elevation view of the seat assembly station illustratedin FIG. 1.

FIG. 3 is front elevation view of the seat assembly station illustratedin FIG. 1.

FIG. 4 is a schematic flow/control diagram for an continuous moving lineconveyor type seat assembly station.

FIG. 5 is a schematic flow/control diagram for an intermittent type seatassembly station.

FIG. 6 is an illustration of one type of sensing system for use in anembodiment of the present invention.

FIG. 7 is an illustration of another type of sensing system for use inan embodiment of the present invention.

While the invention will be described in connection with certainpreferred embodiments, there is no intent to limit it to thoseembodiments. On the contrary, the intent is to cover all alternatives,modifications and equivalents as included within the spirit and scope ofthe invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of illustration, a preferred embodiment of the presentinvention has been illustrated in FIGS. 1-4 as embodied in an assemblystation 10 for assembling articles of assembly illustrated in the formof automotive seats 12. Although only one assembly station 10 is fullyillustrated in FIGS. 1-3, it will be appreciated that the assemblystation 10 is one of several assembly stations that are typicallydisposed in a predetermined sequence whereby assembly work operationsare performed.

To transport the seats 12 through the various stations, a conveyor 14 isprovided that runs through the assembly station 10. The conveyor 14 isillustrated as a continuous type in which the conveyor 14 runs and movesthe seats 12 substantially continuously. In particular, the conveyor 14will typically run on a continuous basis and continuously move the seats12 downstream through the various stations unless the necessary workoperations any of the particular stations are not performed within theallotted time given for that station, or a breakdown occurs, or othersimilar event occurs requiring stoppage of the conveyor 14. As can beseen in FIG. 1, the assembly station 10 has a span 16 of work area overwhich the work operations can be performed at the illustrated assemblystation 10. The amount of time a seat 14 typically spends at an assemblystation is equal to the length of the span 16 divided by the operatingspeed of the conveyor 14.

The conveyor 14 includes a stationary support frame 20 and a moving line22. A plurality of seat fixtures 18 are affixed to the moving line 22 atequidistant intervals. The seat fixtures 18 clamp onto or other wisehold the seats 12 in a fixed position for assembly operations.Unassembled base frames of seats 12 are clamped into the fixtures 18(typically through locating pins and a clamping mechanism that are notshown) at the upstream input location of the conveyor 14, while assemblyseats are removed from the fixtures 18 at the downstream output locationof the conveyor 14. The fixtures 18 are recycled and used over and overagain for assembling seats 18.

For purposes of reference, three mutually perpendicular axes 24, 26, 28have been shown. The axes include a horizontal axis 24 parallel to theconveyor 14, a vertical axis 26 and a tool plunging axis 28.

At the illustrated assembly station 10, a fastening tool is provided inthe illustrated form of an electrically powered, torque reaction arm,screw driver 30 (“power screw driver”) for driving threaded bolts,screws or other threaded fasteners into the frame 13 of the seat 12. Thepower screw driver 30 is manually operated including a handle 32 and atrigger 34 that provides for forward and reverse modes tocorrespondingly drive or remove threaded fasteners. The power screwdriver 30 also comprises an integral torque monitor 31 that is capableof providing an output of the torque applied to fasteners by the powerscrew driver 30.

The power screw driver 30 is mounted on a horizontal tool platform 36via a first linear rail mechanism 38 that extends the tool plunging axis28. The first linear rail mechanism 38 allows for sliding linearmovement of the driver 30 in the plunging axis 28. The horizontal toolplatform 36 is in turn supported by a second linear rail mechanism 40that extends in the vertical axis 26. The second linear rail mechanism40 is mounted to a vertical support plate 42. The second linear railmechanism 40 allows for sliding linear movement of the driver 30 in thevertical axis 26. A supporting recoil cylinder 44 may be used to supportthe horizontal platform 36 at the desired height and to counteract theforce of gravity for the support assembly of the driver. The verticalsupport plate 42 is in turn supported by a third linear rail mechanism46 that is mounted to an adjacent wall or side 48 of the conveyor 14.The third linear rail mechanism 46 allows for sliding linear movement ofthe driver 30 in the horizontal axis 24 parallel to the length of theconveyor 14 at the assembly station 10. The length of the third linearrail mechanism 46 also determines and sets the span 16 of the assemblystation 10 over which fastening operations can be performed with thepower screw driver 30. From the foregoing, it can be seen that the powerscrew driver 30 can be manipulated along the three different axes 24,26, 28, relative to the conveyor 14 and or fixtures 18 to fasten screwsinto seats 12 as desired.

In accordance with the present invention, the disclosed embodimentincludes a plurality of differentiated targets 50a, 50b, 50ccorresponding to different fastening locations 52a, 52b, 52c on the seat12, respectively, and a target sensor in the form of a machine visioncamera 54 for sensing the targets 50a-c. The camera 54 is fixed relativeto the power screw driver 30 in at least one axis, up to all three axes.For example the target sensor camera 54 may be mounted to the horizontalplatform 36 and is therefore fixed relative to the power screw driver 30in the vertical and horizontal axes 24, 26.

The individual targets 50a-c are fixed relative to the seat 12 in spacedapart relation to their respective fastening locations 52a-c on the seat12. The spaced apart relation is substantially the same between each ofthe targets 50a-c and corresponding fastening locations 52a-c in termsof distance (horizontal and vertical) and angular orientation. Thisequidistant spacing is also substantially the same as that between thetip end of the power screw driver 30 and the machine vision camera 54.In this manner, and with the camera 54 aligned parallel to the toolplunging axis 28, the machine vision camera 54 will sense the firsttarget 50a when the power screw driver 30 is at the first fasteninglocation 52a, will sense the second target 50b when the power screwdriver 30 is at the second fastening location 52b, and will sense thethird target 50c when the power screw driver 30 is at the thirdfastening location 52c.

To fix the targets 50a-c relative to the seat 18, the targets 50a-c arepreferably provided on panels 56 that in turn are mounted to the eachone of the fixtures 18. The targets 50a-c may also be mounted to themoving line 22 of the conveyor (since the conveyor moves at the samespeed as the seats) or mounted to or integrally provided by the seats 18themselves to provide for fixed targets relative to the seats. Forintermittent stop and go systems, the targets may be fixed stationary atthe assembly station such as to the stationary support frame of theconveyor because the seat is stopped in position while work operationsare being performed.

As shown in FIG. 1, each of the targets 50a-c has a distinctivecharacteristic that is different than that of the other targets 50a-c,which allows for differentiation of the targets 50a-50c. In FIG. 1 thedistinctiveness is provided through different angular orientations of alarge bolt head target and a small bolt head target. The machine visioncamera 54 generates an electronic output that differentiates between thedifferent targets 50a-50c. This electronic output of the machine visioncamera 54 is communicated to a processor or electronic controller 58.

The electronic controller 58 has several outputs and inputs and canutilize the electronic output from the machine vision camera 54 for avariety of purposes such as sounding an alarm, stopping the conveyor 14and/or collecting data for analysis or quality control purposes. Theactual purpose may vary between applications.

In continuous conveyor seat assembly systems where certain screw torquesor fastening sequences may be critical, the electronic output from themachine vision camera 54 may be used to stop the conveyor 14 in theevent that not all fastening operations are performed correctly asrequired, to allow further time to finish those operations at theillustrated assembly station 10. Although this can stop the entireconveyor line and affect other upstream or downstream stations, thedisclosed embodiment ensures fool-proof assembly that ensures thatproper fastening torques at each of the fastening locations 52a-c and/orfastening sequences at the fastening locations 52a-c is achieved with nofurther quality control required over fastening operations. In typicalassembly line set ups, the conveyor line 22 will be moving at a speedthat is typically sufficient to allow all work to be accomplished in theallotted time at each of the assembly stations along the conveyor.

At the illustrated assembly station 10 of FIG. 1, the electroniccontroller 50 has an position sensor input indicating when seats 12enter and are about to leave the assembly station 10. This input mayinclude a first proximity sensor 60 located near the entrance to theassembly station 10 for indicating when a seat is about to enter thestation 10 and includes a second proximity sensor 62 located near theexit of the assembly station 10 for indicating when a seat is about toleave the station 10. The electronic controller 50 also has a connectionto the conveyor drive 64 that is operable to stop the moving line 22 ofthe conveyor 14. The electronic controller 50 also has a connection tothe torque reaction arm or driver 30 for activating the driver 30 whenthe driver 30 is in a proper fastening position and disabling the driver30 when the driver 30 is not in a proper position to fasten at one ofthe fastening locations 52a-c. The electronic controller 50 alsoreceives feedback from a torque monitor 31 integral with the driver 30to provide an indication of the driven torque applied at a fasteninglocation.

For purposes of illustration, one form of an operational electroniccontrol diagram with a continuous conveyor system is illustrated in FIG.4. As shown in FIG. 4 with continuing cross reference with FIG. 1, acontinuous conveyor system preferably includes two different types ofseat fixtures 18, 19 which hold the same seat but are differentiated byvirtue of the fact that they have different types of the first, secondand third targets 50a-50c, 51a-51c. In this manner, if the fixturespacing along the conveyor 14 is such that more than one fixture may beat the assembly station 10 within its span 16 at a given moment, themachine may not be tricked by moving the driver 30 from the seat of theleading fixture 18 to the seat of the trailing fixture 19 and fasteningthe location(s) that are missing from the seat held in the leadingfixture 18.

In any event, the program is started by first monitoring fixtureposition 100 in response to the fixture position sensor 62 to ensurethat the leading fixture 18 has not left the station 10 with a seat 12without proper fastening at each of the three fastening locations52a-52c. It is determined whether a fixture has left or is about toleave the assembly station without proper fastening at all threelocations (e.g. setting flags as will be described) 102. If not allfastening locations have been properly fastened, then the electroniccontroller sends a stop signal 104 to the conveyor drive 64 to stop theconveyor 14 to ensure that all necessary fastening operations can becompleted.

If, however, there is still time to conduct fastening operations, thenthe tool position is monitored 106 to determine whether the fasteningtool or driver 30 is at a fastening location 108. If the fastening toolor driver 30 is not in position, then the fastening tool is disabled110. If, however, the driver 30 is in position in front of one of thefastening locations as indicated by one of the six targets, then thefastening tool is enabled 112. The driver torque may then be monitored114. The input received from the position sensor 54 is also evaluatedbased on the differentiating characteristics of the various targets50a-50c, 51a-51c to determine tool position 116 and first whether thetool is servicing either fixture A 18 or fixture B 19 and then whetherthe tool is in the first fastening position, the second fasteningposition, or the third fastening position as indicated by schematicblocks 120, 122, 124. There are similar sequences run for both fixturesA and B as indicated, but only one sequence is for fixture A is shown tosimplify the drawings.

As shown, once the tool fastening position is determined, then theelectronic controller 58 determines whether the torque value has beenreached for that position as indicated by schematic blocks 126, 128, and130. If the torque value has been reached as previously monitored inschematic block 114, then a torque flag is set representing thatfastening location as indicated in schematic blocks 132, 134, 136.Thereafter, all torque flags are monitored 138 to determine whether allthree torque flags representing the three different fastening locationshave been set 140. If all torque flags have been set, then the fixtureis allowed to leave the station 10 and all of the flags for fixture typeA are reset 142 and the system can be recycled 144. If however, not allthree torque flags have been set 140, then the entire process isrecycled back to the beginning and the fixture position is again sensed100.

It will be appreciated that all of the operations indicated in FIG. 5from start to end take only a fraction of a second and therefore, thiscycle may be run tens or hundreds of times every second to update thetorque values indicated in blocks 132, 134, and 136 on an instantaneousbasis. It will also be appreciated that with the continuous type systemthat two different types of fixture targets need not be supplied if thefixtures 18, 19 are sufficiently spaced apart such that only one fixtureoccurs over the working span 16 of the assembly station 10 at any giventime or that it is unlikely that a worker would switch between the seatsheld by leading and trailing fixtures. A further advantage of having twodifferent types or sets of targets 50a-50c and 51a-51c is that differenttypes of seats with different fastening requirements may be run throughthe station on the same continuous line if desired. Currently this isnot practiced and each line is dedicated to a single model or type ofseat 12. It will also be appreciated in viewing FIG. 4 that the generallogic used in the electronic controller is indicated and that the exactsequence illustrated in FIG. 4 is not necessarily required. However,FIG. 4 represents the various electronic connections of the electroniccontroller 58 and the determinations and inputs and outputs conducted bythe electronic controller 58.

Further features may also be added. For example, a further feature thatcan be used which is not illustrated in FIG. 4 is that once a flag isachieved for one of the given fastening locations 52a-c, the driver 30may be disabled when it is indicated the driver 30 is in front of thatposition. This prevents a worker from operating the driver in reverseand removing a properly fastened bolt. The electronic controller 50 mayalso or alternatively have a predetermined sequence program requiring apredetermined sequence of fastening among the fastening locations 52a-c.According to this feature, the electronic controller controls thesequence of fastening based upon the target output and provides asequence output indicating whether the predetermined sequence has beenachieved. This may simply entail ensuring that the driver 30 is activeonly when in front of the correct one of the fastening locations 52a-cas indicated by the respective targets 50a-c.

Turning then to FIG. 5, a control and flow diagram for an intermittentconveyor system is illustrated whereby seat fixtures 200 would bestopped at the assembly station while the work operations are performedat that station and not released until all work operations have beensuccessfully completed. According to this system, the electroniccontroller monitors fixture position 202 based on output from a fixtureposition sensor 204 which indicates whether or not the seat fixture 200has arrived at a fixed stopped position along the intermittent conveyorsystem (not shown). The system determines first whether the fixture 200is in place 206. If the fixture 200 is not in place, then the fasteningtool 208 is disabled 210 and the cycle is restarted. Once the fixture,however, is in place, then the output from a tool position sensor 212 ismonitored 214. In particular, the tool position sensor 212 senses one ofthree targets 213-215 provided on the seat fixture 200. Each of thesetargets 213-215 has a different characteristic such that the outputprovided by the tool position sensor 212 has a different characteristicthat can be monitored 214 by the electronic controller. Because thefixture is in place 206, the fastening tool may be enabled 216 (oralternatively enablement of the fastening tool may depend upon whetherthe fastening tool 208 is at a proper fastening location as indicated bythe tool position sensor 212). The electronic controller then monitorstorque 218 as indicated by the tool torque monitor 220 of the fasteningtool 208. Based on the sensed position sensor input from the toolposition sensor 212, the electronic controller can then interpret theposition sensor input to determine the tool position 222 to determinewhether it is positioned to fasten a fastener at one of the threefastening locations. Thereafter, depending upon whether the tool is infastening position one, two, or three 223-225, the electronic controllerwill compare the monitored torque 218 to a predetermined torque value227-229 and if appropriate set a torque flag 230-232 for the first tothird fastening locations, respectfully. The electronic controllermonitors all torque flags 235 to determine whether appropriate torquevalues for all three fastening locations has been set 237. If so, thetorque flags may be reset 239 the fastening tool disabled 241 and theconveyor can be activated to move the fixture holding the seat out ofthe assembly station 243, and the process can be started again once anew seat and seat fixture 200 enter the assembly station. If, however,not all three torque flags have been set 237, then the process isrecycled to again run through each of the steps until all three torquevalues have been reached as indicated by the torque flags 230-232thereby indicating that all work operation have been properly performedand that the seat and fixture are ready for further downstream workoperations if appropriate.

The target and target sensor assembly of the system is illustrated inFIG. 6. As shown, the targets may comprise two bolts at differentangular orientations among the various targets 50a, 50b, 50c. Themachine vision camera 54 has an output representing the targets that canbe interpreted by the electronic controller 50 and used fordifferentiation determinations. Although two different geometric shapeshave been illustrated as the targets, it will be appreciated that thetargets may be selected from the group consisting of geometric shapes,colors and alphanumeric characters.

A second embodiment of a sensing system is shown in FIG. 7. According tothis system a laser emitter and receiver device 300 is utilized inassociation with reflective panel(s) which may include separate panelsor a single inclined reflective panel 302 as illustrated. According tothis embodiment, the individual targets 304 comprise spaced apartsections of the reflective material which are at different distancesalong the plunging axis relative to the emitter and receiver device 300.Because reflection and distance among the plunging axis is critical forthis embodiment, as the fastening tool plunges along a fastening axis,the laser and laser sensing device remaining stationary during plungingof the fastening tool to keep the targets 304 at the desired distancefrom the laser emitter and receiver device 300.

It should be noted that a minimum of two different fastening locationsand targets as described above are necessary for the subject invention.It will readily be appreciated to those skilled in the art that anynumber of targets and fastening locations above two may be used and arespecifically intended to be covered by all of the claims appendedhereto.

It should also be noted that the present position monitoring system mayalso incorporate a sensor, linear transducer or laser to monitor thetool position to determine bolt position in the vertical axis 26. Forexample, bolts on the seats carried on the conveyor are always at aconstant known elevation. As such, if bolts are at different elevations,and, if a fixed angle, 90 degree driver/tool is being used (rather thana tool that pivots), then sensing tool elevation provides an indicationof the particular bolt being serviced. This may also be used todetermine cross line or plunging travel of the tool in the plunging axis28, and thus used to differentiate bolts spaced at different spacing inthe plunging axis 28. The electronic controller 58 may use feedback fromsuch tool position sensors to determine the fastening location beingserviced in addition to the target sensing system feedback.

Although a laser sensor and machine vision camera sensor have been shownin FIGS. 6 and 7 of a preferred embodiment, it will be appreciated thatother sensors and targets may also be utilized and are covered bycertain claims appended hereto. For example, a bar code scanner couldact as the sensor with bar codes used for targets.

The disclosed position system can also be used to set differentparameters for each bolt. The parameters include run down speed,acceleration, deceleration, and the final torque target value. This isvaluable because it helps to proactively prevents bad run downs whichslow down the assembly process.

All of the references cited herein, including patents, patentapplications, and publications, are hereby incorporated in theirentireties by reference.

The foregoing description of various embodiments of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the preciseembodiments disclosed. Numerous modifications or variations are possiblein light of the above teachings. The embodiments discussed were chosenand described to provide the best illustration of the principles of theinvention and its practical application to thereby enable one ofordinary skill in the art to utilize the invention in variousembodiments and with various modifications as are suited to theparticular use contemplated. All such modifications and variations arewithin the scope of the invention as determined by the appended claimswhen interpreted in accordance with the breadth to which they arefairly, legally, and equitably entitled.

What is claimed is:
 1. A method for assembling an article of assembly,the article of assembly having a plurality of fastening locationsincluding first and second fastening locations in spaced apart relation,comprising: holding the article of assembly in a predetermined position;providing a plurality of targets including at least a first target fixedrelative to the article of assembly corresponding to the first fasteninglocation of the article of assembly and a second target fixed relativeto the article of assembly corresponding to the second fasteninglocation, the second target having a different characteristic than thefirst target; manually fastening fasteners into the article of assemblyat the first and second fastening locations; and sensing the first andsecond targets when said fastening is occurring at the first and secondlocations, respectively, and generating an electronic target outputbased upon said sensing that differentiates between the first and secondtargets thereby indicating when a fastening tool is in either of thefirst and second fastening locations.
 2. The method of claim 1 furthercomprising conveying the article of assembly through an assemblystation.
 3. The method of claim 2 further comprising: intermittentlystopping the article of assembly at the assembly station for saidfastening; and monitoring the location of said fastening to ensureproper fastening of fasteners at the fastening locations.
 4. The methodof claim 3 further comprising: maintaining the fixture at the assemblystation and not releasing the fixture for further conveying out of theassembly station until the fastening tool has properly fastenedfasteners into the article of assembly at the first and second fasteninglocations.
 5. The method of claim 4, wherein the fasteners are threadedfasteners, further comprising: measuring torque applied to thefasteners; electronically indicating measured torque applied to thefasteners at at least one of the fastening locations; determining thelocation of said fastening that corresponds to the indicating ofmeasured torque; electronically comparing measured torque withpredetermined torque values for the at least one of the fasteninglocations; and providing an output indicating whether the predeterminedtorque values for at least one of the fastening locations have beenreached.
 6. The method of claim 5, further comprising: releasing thearticle of assembly and conveying the article of assembly out of theassembly station when the predetermined torque values have been reached.7. The method of claim 1, further comprising: monitoring a sequence ofsaid fastening; electronically comparing the monitored sequence with apredetermined sequence of fastening among the fastening locations; andproviding a sequence output indicating whether the predeterminedsequence has been achieved.
 8. The method of claim 2 further comprisingtransporting the articles of assembly through the assembly stationsubstantially without stopping on a continuous basis.
 9. The method ofclaim 8, further comprising: providing at least two types of first andsecond targets, each different type corresponding to one of the articlesof assembly; generating said target output that differentiates betweenthe at least two types of first and second targets; and electronicallydetermining the article of assembly subject to said fastening bydifferentiating between the different types of the first and secondtargets.
 10. The method of claim 8 wherein the assembly station has aninput location receiving fixtures from an upstream station and an outputlocation delivering fixtures to a downstream station, wherein saidfastening is conducted in a range between the input location and theoutput location, further comprising: electronically sensing whenarticles of assembly are exiting the assembly station and providing afixture position output indicating when fixtures have exited theassembly station through the output location; electronically determiningwhether said fastening has been properly conducted on each article ofassembly exiting the assembly station; and outputting an electronicalarm signal when one of the articles of assembly has exited theassembly station without proper fastening at the first and secondfastening locations.
 11. The method of claim 10, further comprisingtemporarily stopping the conveying of the articles of assembly inresponse to the electronic alarm signal so corrective action may beperformed on the article of assembly.
 12. The method of claim 10,wherein the fasteners are threaded fasteners, wherein said properfastening comprises: measuring torque applied to the fasteners;electronically indicating measured torque applied to the fasteners at atleast one of the fastening locations; determining the location of saidfastening that corresponds to the indicating of measured torque;electronically comparing measured torque with predetermined torquevalues for the at least one of the fastening locations; and providing anoutput indicating whether the predetermined torque values for at leastone of the fastening locations have been reached.
 13. The method ofclaim 10 wherein said proper fastening comprises: monitoring a sequenceof said fastening; electronically comparing the monitored sequence witha predetermined sequence of fastening among the first and secondfastening locations; and providing a sequence output indicating whetherthe predetermined sequence has been achieved.
 14. The method of claim 10further comprising: assigning adjacent articles of assembly differenttypes of the first and second targets for purposes of differentiationaccording to a predetermined fixture sequence; determining the articleof assembly subject to fastening operations based upon the predeterminedsequence.
 15. The method of claim 1 wherein said sensing is accomplishedwith a machine vision camera and wherein the targets have differentvisual characteristics, further comprising electronicallydifferentiating between the different visual characteristics containedin the electronic target output to determine the location of thefastening tool.
 16. The method of claim 15 wherein the targets areselected from the group consisting of geometric shapes, colors andalphanumeric characters.
 17. The method of claim 2 wherein said sensingis accomplished with a laser and laser sensing device, said fasteningbeing accomplished with the fastening tool movable in a plane spacedfrom the article of assembly to selectively position the fastening toolat the fastening locations, the laser and laser sensing device beingmovable with the fastening tool in said plane, the targets comprisingreflective material spaced at different distances perpendicular to saidplane.
 18. The method of claim 17 wherein the fastening tool plungesalong a fastening axis perpendicular to said plane, the laser and lasersensing device remaining stationary during plunging of the fasteningtool.
 19. The method of claim 18 wherein the article of assembly iscarried by a conveyor, the fastening tool being movable horizontallyrelative to the conveyor, the laser and laser sensing device beingrestricted to horizontal movement along a horizontal axis along with thefastening tool, further comprising a reflective panel extending in thehorizontal axis in reflective communication with the laser and lasersensing device with a reflective surface aligned at an oblique anglerelative to said plane providing the targets.
 20. The method of claim 1wherein the article of assembly comprises an automotive seat comprisedof at least two parts, the fasteners comprising threaded fasteners forfastening the at least two parts together.
 21. The method of claim 1further comprising: enabling the fastening tool when one of the targetsis sensed; and disabling the fastening tool when none of the targets aresensed.
 22. A method for assembling an article of assembly, the articleof assembly having a plurality of fastening locations including firstand second fastening locations in spaced apart relation, comprising:holding the article of assembly in a predetermined position; manuallyfastening fasteners into the article of assembly using a fastening toolat the first and second fastening locations according to a predeterminedfastening sequence; sensing the position of the fastening tool;electronically comparing the sensed position of the fastening tool witha predetermined sequence of fastening among the first and secondfastening locations; and providing a sequence output indicating whetherthe predetermined sequence has been achieved.
 23. The method of claim22, wherein the article of assembly comprises a vehicle seat.
 24. Themethod of claim 22, further comprising enabling the fastening tool whenthe fastening tool is at one of the first and second locations and apredetermined fastening sequence is followed, and disabling thefastening tool when the predetermined fastening sequence is notfollowed.
 25. The method of claim 24, further comprising disabling thefastening tool when not at a fastening location.
 26. The method of claim24, further comprising monitoring torque applied during said manualfastening, providing an electronic torque output indicating whether atleast one predetermined torque value has been reached.
 27. The method ofclaim 26, enabling the fastening tool when the fastening tool is at oneof the first and second locations and a predetermined fastening sequenceis followed, and disabling the fastening tool when the predeterminedfastening sequence is not followed.
 28. The method of claim 27, furthercomprising disabling the fastening tool when a predetermined torquevalue is not reached for one of the fastening locations in thepredetermined sequence and the fastening tool is at a fastening locationother than said one of the fastening locations.
 29. The method of claim22, wherein said sensing comprises sensing targets including first andsecond targets arranged in relation to the first and second fasteninglocations, the first and second targets being sensed when said fasteningis occurring at the first and second fastening locations, respectively;and generating an electronic target output based upon said sensing thatdifferentiates between the first and second targets thereby indicatingwhen the fastening tool is in either of the first and second fasteninglocations.
 30. The method of claim 29, wherein said sensing is conductedwith one of a machine vision camera and a laser sensing device.
 31. Amethod for assembling components of an article of assembly, the methodcomprising the steps of: providing at least first and second physicallyseparate components that, when assembled together, form at least aportion of the article of assembly, wherein (a) a single set of discreteportions of the first and second components, when placed together, forma single process site consisting of a plurality of fastening locationswithin the single process site including first and second fasteninglocations, (b) each of the first and second fastening locations consistsof a single opening for receiving a single fastener that, when fastenedin the single opening, partially assembles the first and secondcomponents together, and (c) wherein the article of assembly isstructurally designed so that the first and second fastening locationsare positioned within the single process site in spaced apart relationto each other such that a fastener must be inserted in the firstfastening location before a fastener is inserted in the second fasteninglocation to reduce the risk of structural failure of the assembledcombination of the first and second components that would arise if afastener were inserted in the second fastening location before afastener were inserted in the first fastening location, holding thefirst and second components of the article of assembly in apredetermined position in which the first and second components areplaced together to form the single process site; manually fasteningfasteners into the first and second fastening locations of the articleof assembly using a fastening tool; providing an electronic controllerhaving stored in a memory thereof before an operator has commenced anyaspect of manually fastening fasteners using the fastening tool (a) datarepresentative of the location of the first fastening location withinthe single process site together with first order data indicating that afastener must be inserted in the first fastening location at a point intime before a fastener is inserted in the second fastening location, and(b) data representative of the location of the second fastening locationwithin the single process site together with second order dataindicating that a fastener must be inserted in the second fasteninglocation at a point in time after a fastener has been inserted in thefirst fastening location, wherein the location data and the first andsecond order data for the first and second fastening locations from apredetermined fastening sequence that must be followed in order for thefirst and second components to be assembled together in a manner thatreduces the risk of structural failure of the assembled combination thatwould arise if a fastener were inserted in the second fastening locationbefore a fastener were inserted in the first fastening location; sensingthe position of the fastening tool; electronically comparing the sensedposition of the fastening tool with the data representative of thelocation of the first and second fastening locations to determine if thefastening tool is located in operative relation to one of the first andsecond fastening locations and then using the order data associated withthe one of the first and second fastening locations to ensure theoperator's use of the fastening tool conforms to the predeterminedsequence of fastening among the first and second fastening locations by(a) enabling the fastening tool, when it is positioned in operativerelation to the first fastening location, to insert a fastener in thefirst fastening location only if the operator has not inserted afastener in the second fastening location, and (b) enabling thefastening tool, when it is positioned in operative relation to thesecond fastening location, only if the operator already has inserted afastener in the first fastening location, which reduces the risk ofstructural failure of the assembled combination that would arise if afastener were inserted in the second fastening location before afastener were inserted in the first fastening location; providing asequence output each time that the operator attempts to fasten afastener in one of the first and second fastening locations indicatingwhether the predetermined fastening sequence has been achieved; whereinthe electronic controller also has stored in its memory first and secondpredetermined torque values that represent torque values that theoperator is supposed to apply to fasteners inserted in the first andsecond fastening locations when the operator's use of the fastening toolconforms to the predetermined sequence of fastening; and when theoperator's use of the fastening tool conforms to the predeterminedsequence of fastening, (a) measuring torque applied to fastener by thefastening tool as it is being fastened in the first fastening locationand then comparing the measured torque to the first predetermined torquevalue, (b) requiring that the torque applied to the fastener located inthe first fastening location equal the first predetermined torque valuebefore the operator is allowed to insert a fastener in the secondfastening location, which reduces the risk of structural failure of theassembled combination that would result if the operator were allowed toinsert a fastener in the second fastening location when the torqueapplied to the first fastener does not equal the first predeterminedtorque value, (c) measuring torque applied to a fastener by thefastening tool as it is being inserted in the second fastening locationand then comparing the measured torque to the second predeterminedtorque value, and (d) requiring that the torque applied to the fastenerlocated in the second fastening location equal the second predeterminedtorque value after the first fastener has been inserted in the firstfastening location at the first predetermined torque value, whichreduces the risk of structural failure of the assembled combination thatwould result if the operator were allowed to complete assembly of thefirst and second components when the torque applied to the fastenerinserted in the second fastening location did not equal the secondpredetermined torque value.
 32. The method of claim 31, wherein theelectronic comparison step also includes disabling the fastening toolfrom performing a fastening operation when it is located at the firstfastening location if the operator already has applied a first fastenerin the first fastening location with a torque that equals the firstpredetermined torque.
 33. The method of claim 32, wherein the article ofassembly comprises a vehicle seat.
 34. The method of claim 31, furthercomprising the step of disabling the fastening tool when it is notdisposed in operative relation to a fastening location.
 35. The methodof claim 31, wherein the first component comprises a seat track.
 36. Themethod of claim 31, wherein the first component comprises a base frame.37. The method of claim 31, wherein each fastener consists of a threadedfastener.
 38. The method of claim 37, wherein each threaded fastenerconsists of a threaded bolt.
 39. The method of claim 31, wherein thefirst and second components of the article of assembly are provided bymeans of a continuous moving line conveyor.
 40. The method of claim 31,wherein the first and second components of the article of assembly areprovided by means of an intermittent conveyor line.
 41. The method ofclaim 31, wherein the first and second components are mounted on anunassembled base frame.
 42. The method of claim 41, wherein the holdingstep comprises clamping the unassembled base frame into a fixture. 43.The method of claim 42, wherein the fixture and unassembled base frameare provided by means of a continuous moving line conveyor.
 44. Themethod of claim 42, wherein the fixture and unassembled base frame areprovided by means of an intermittent conveyor line.
 45. The method ofclaim 31, wherein a third fastening location is positioned in spacedapart relation to the first and second fastening locations, the thirdfastening location consisting of a single opening for receiving a singlefastener.
 46. The method of claim 45, wherein the predetermined sequenceof fastening is for all of the first, second, and third fasteninglocations.
 47. The method of claim 31, wherein the fastening tool formsa part of an assembly station, the method further comprising the step ofrequiring the first and second components to remain in the assemblystation until after it is verified that (a) the operator's use of thefastening tool conformed to the predetermined sequence of fastening forthe single process site, and (b) torque values equal to the first andsecond predetermined torque values were applied to fasteners located inthe first and second fastening locations when the operator's use of thefastening tool conformed to the predetermined sequence of fastening forthe single process site.
 48. The method of claim 47 further comprisingthe step of producing an alarm simultaneously with when an attempt ismade to remove the first and second components from the assembly stationbefore it is verified that (a) the operator's use of the fastening toolconforms to the predetermined sequence of fastening for the singleprocess site, and (b) torque values equal to the first and secondpredetermined torque values were applied to fasteners located in thefirst and second fastening locations when the operator's use of thefastening tool conformed to the predetermined sequence of fastening forthe single process site.
 49. The method of claim 48 wherein the assemblysystem further comprises a stop mechanism that requires the first andsecond components to remain in the assembly station.
 50. The method ofclaim 49, wherein the stop mechanism prevents removal of the first andsecond components from the assembly station.
 51. The method of claim 50,wherein the first and second components are carried by a conveyor intoand out of the assembly station the movement of which is stopped by thestop mechanism.
 52. The method of claim 51, wherein the conveyorcomprises an intermittent conveyor.
 53. The method of claim 51, whereinthe conveyor comprises a continuous conveyor.
 54. The method of claim31, wherein the first and second components comprise components of avehicle seat.
 55. The method of claim 48, wherein the alarm is given asa result of the attempt to remove the first and second components of theassembly station.